A brain-penetrant chimeric protein combines direct glioma targeting with myeloid cell-mediated immune reprogramming

Glioblastoma (GB) is the most aggressive primary brain tumor, characterized by poor prognosis, profound immunosuppression, and limited response to current therapies. To overcome these barriers, we developed CTX-CNF1, a brain-penetrant recombinant protein that integrates direct glioma targeting with myeloid cell–mediated immune reprogramming. CTX-CNF1 was generated by fusing Chlorotoxin (CTX), which enables selective delivery across the blood–brain barrier, with Cytotoxic Necrotizing Factor 1 (CNF1), a bacterial protein with antitumor and immunostimulatory properties. Therapeutic efficacy was evaluated in immunocompetent orthotopic GB mouse models using survival analysis, MRI, motor assessment, and immunophenotyping. Systemic CTX-CNF1 administration was well tolerated and significantly prolonged survival, reduced tumor burden, and preserved motor function. A substantial proportion of treated animals achieved complete tumor regression and resisted tumor re-challenge, consistent with the induction of durable antitumor immunity. Mechanistically, CTX-CNF1 promoted a pro-inflammatory reprogramming of tumor-associated myeloid cells and enhanced CD8⁺ T-cell recruitment and cytotoxicity, thereby counteracting GB-associated immunosuppression. Therapeutic efficacy was confirmed across distinct glioma models. In combination settings, CTX-CNF1 selectively enhanced the activity of immune checkpoint blockade in a context-dependent manner. CTX-CNF1 represents a dual-action therapeutic strategy that combines tumor targeting with immune modulation and effective brain delivery. By coupling direct antitumor effects with remodeling of the tumor immune microenvironment, CTX-CNF1 supports the development of combinatorial approaches to overcome therapeutic resistance in GB and other immune-cold tumors.